Piston pump



July 20, 1954 Filed July 16, 1949 J. P. JOHNSON PISTON PUMP 3 Sheets-Sheet l [4 T IS 8 l3 2 Jamar-5 P. JOHNSON 5M1 IMP/4 July 20, 1954 J. P. JOHNSON 2,684,038

PISTON PUMP Filed July 16, 1949 Sheets-Sheet 2 60 7 57 6o 719.7 6 7 9 s3 93 80 I00 86 103 INVENTOR.

Y JAMES P. Ja /v50 A T ENE 76.

J. P. JOHNSON PISTON PUMP July 29, 1954 5 Sheets-Sheet 3 Filed July 16, 1949 ATTOR/x/E Y5.

Patented July 20, 1954 UNITED STAT TENT OFFICE 20 Claims.

The present invention relates generally as indicated to a piston pump and has for one of its primary objects the provision of a piston pump which is of simple fool-proof construction and of high mechanical and volumetric efficiency and which for a predetermined over-all size of unit has a considerably larger displacement than gear or vane type pumps of comparable size.

Other objects and advantages will become apparent as the following description proceeds.

To the accomplishment of the foregoing and related ends, said invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawings settin forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principle of the invention may be employed.

In said annexed drawings:

Fig. 1 is a cross-section view of one embodiment of this invention taken substantially along the line I-I, Fig. 2;

Fig. 2 is a cross-section view taken substantially along the line 2-2, Fig. 1;

Fig. 3 is a perspective view of the intersecting and nested pistons employed in the Fig. 1 unit;

Fig. 4 is a cross-section view similar to Fig. 1 except illustrating a modification;

Fig. 5 is a perspective view of the intersecting pistons employed in the Fig. 4 unit;

Fig. 6 is a cross-section view taken substantially along the line 6-6, Fig. 7 of a still further modification;

Fig. '7 is a cross-section view taken substantially along the line l'l, Fig. 6;

Fig. 8 is a cross-section view of a modification taken substantially along the line 8--8, Fig. 9;

Fig. 9 is a cross-section view taken substantially along the line as Fig. 8;

Fig. 10 is a cross-section view taken substantially along the line lit-4t, Fig. 9;

Fig. 11 is a cross-section view of a still further modification taken substantially along the line 11-, Fig. 12;

Fig. 12 is a cross-section view taken substantially along the line l2i2, Fig. 11;

Fig. 13 is an end elevation view as viewed from the right-hand end of Fig. 11; and

Fig. 14 is a cross-section View somewhat diagrammatic of a modification with multiple pistons so arranged as to balance the loads on the drive shaft.

In the embodiment of the invention illustrated in Figs. 1-3 there is provided a pump case comprising the case parts I and 2 bolted or otherwise secured together and defining therebetween a cylindrical chamber comprising parallel end walls 3 and t and a cylindrical bore 5, said bore being intersected at circumferentially spaced points by the ports 6 and i formed in the case part 2.

Non-rotatably fitted in such chamber is a liner sleeve or stator 8 preferably of bearing metal provided with slots 9 and m transversely through the wall thereof, said slots respectively communicating with the ports 5 and i. The walls 3 and l of the case parts I and 2 may also be lined with plates H and I2 of bearing metal.

Having a free-running and sealed fit within said liner 8 and also with the plates H and I2 is a piston-carrying member or rotor E3 of hollow cylindrical form having an inner surface formed with two pairs of diametrically opposed and radially disposed grooves M- spaced apart and extending axially therethrough, said grooves providing piston chambers and being most readily and inexpensively formed as by broaching, for example. Said rotor 53 is further formed with a corresponding number of uniformly spaced openings l5 radially through the wall thereof and leading to the respective grooves 14 and adapted to alternately communicate with the slots 9 and It in sleeve 8 during rotation of said rotor in said sleeve.

Diametrically across said rotor I3 and mounted in each pair of grooves or piston chambers M for reciprocation therein radially of said rotor is a piston 16 comprising, as best shown in Fig. 3, a head it at each end having a sliding seal with the side walls of the respective grooves it and a cut-away central portion l8 permitting intersection and nesting of the two pistons and independent reciprocation thereof along perpendicularly disposed paths. Each said piston It is further formed with a centrally disposed rectangular opening l9 axially therethrough, the short sides of such opening being parallel to the radial path of reciprocation of the piston in its pair of grooves I4.

Extending through a boss 29 in the case part i is a drive shaft 2! having a square cross-section end portion 22 non-rotatably but transversely slidably extending into the openings la in said pistons it whereby rotation of said shaft will. through the pistons, effect rotation of the rotor l3 in sleeve 8.

Accordingly, the drive shaft 2! has a nonrotatable and transversely slidable connection with each piston l6, such transverse sliding being along the long sides of each opening It or in other words along a path perpendicular to the radial path of reciprocation of the respective pistons.

As apparent, if said shaft 2| is coaxial with the rotor |3, driving of rotor It through pistons It will not effect any reciprocation of the pistons in piston chambers l4 radially of said rotor and accordingly the pump will then have zero displacement. On the other hand, it can be seen that if said shaft rotates about an axis eccentric to the central axis of rotor l3 and sleeve 8 as shown, not only will said rotor be rotated but said pistons it will be reciprocated radially of said rotor to draw fluid into the piston chambers It and openings l5 which are in communication with one of the slots 9. or and to discharge fluid from the chambers which are in communication with the other of said ports 5 or ill. As illustrated, during rotation of drive shaft 2| and rotor IS in a clockwise direction as viewed in Fig. 1, the chambers I4 will progressively expand in volume while in communication with the port 6 and slot Q whereas the expanded chambers l4 will progressively decrease in volume while in communication with the port E and slot i9. Obviously, if said drive shaft 2| is rotated counter-clockwise, fluid will be drawn in through port I and discharged through port 6.

It will further be apparent to those skilled in the art that the unit illustrated in Figs. 1-3 may be operated as a fluid motor if desired, in which case fluid under pressure entering one of the ports 3 or i will cause rotation of the rotor i3 and shaft 2| and actuation of pistons iii to discharge fiuid from the other one of the ports 5 or Moreover, because the rotation of sleeve 8 and rotor l3 is relative, said drive shaft 2| may be fixed against rotation and said sleeve 8 rotated about rotor I3.

In order to vary the displacement of the unit, the drive shaft 2| is journalled in a bearing 23 in the boss 28 of case part i, said bearing and shaft being shiftable laterally of the axis of rotor i3 and sleeve 8 as by means of the laterally disposed screw 24 having threaded engagement with said bearing and locked in adjusted position as by a screw 25 which is threaded into boss 26 and frictionally clamps a collar portion 26 of screw 2 between one end of the adjusting screw 25 and a shoulder formed in boss 26. In the position of the parts as shown in Figs. 1 and 2 it is apparent that vertical adjustment of shaft 2| will correspondingly shift the vertically disposed piston it, the horizontally disposed piston i6 then being in an intermediate position with the long sides of its rectangular opening |9 vertical for permitting vertical sliding of the square portion 22 of shaft 2| along such long sides.

In the unit illustrated in Figs. 1-3 the displacement per revolution of the rotor l3 will be equal to four times the product of the eccentricity A of the axes of shaft 2| and rotor I3, the width '5 and axial length C of each piston head ll. It is to be noted that because the pistons H3 are nested, the axial length of the unit will be a minimum.

In the form of the invention illustrated in Figs. 4 and 5, the rotor or cylindrical member 3!] comprises an inner sleeve member 3| formed with cylindrical bores or piston chambers 32 diametrically therethrough and 90 apart and an outer sleeve member 33 non rotatably secured to said inner sleeve member as by a screw 35. Said outer sleeve member is formed with openings through the wall thereof spaced 90 apart so as to communicate with the bores or chambers 32 in the inner member 3|.

in this form of the invention, one piston 36 is integrally formed at its opposite ends with coaxial heads 31 of circular cross-section having a close sliding fit in one pair of bores 32 and a web portion 38 connecting said heads together and having one side face passing through the axis of said heads, such web portion 38 being formed with a lateral opening 39 of rectangular cross-section centrally therethrough with the short sides parallel to the aforesaid axis of said heads.

The other piston 49 has circular cross-section and coaxial heads 4| and t2 at opposite ends thereof having a close sliding fit in the other pair of bores 32 in inner member Si and a web portion 13 having one side face coinciding with the axis of the heads 4| and 42 whereby when the pistons 36 and 4B are assembled as in Fig. 5, the axes of the heads 3! and 4| and 2 will intersect with the web portions and 43 in juxtaposed relation. Said web portion 23 also has a rectangular cross-section lateral opening 44 centrally therethrough with its short sides parallel to the axis of heads 4| and In order to facilitate assembly of the pistons 86 and 48 within inner sleeve member 3|, head 42 is detachably connected to the end of the web portion 43 as by a screw 55 which extends through a hole in head 42 and is threaded into the web portion 53. Said web portion and head are preferably provided with complementary interfitting portions whereby to assure proper alignment of said head 42 with head 4|.

As evident, piston will first be inserted through one pair of diametrically opposed bores 32 to a position diametrically across member 3| and piston 4| with head 42 detached will similarly he slid into position in member 3| diametrically across the other pair of bores 32 and finally head 42 will be securely attached by means of screw 45. With the pistons 38 and 58 thus installed in intersecting relation in inner member 3|, outer member 33 may then he slipped over said inner member and locked thereto by screw 34.

The above-described rotor assembly comprising inner member 5| with pistons 36 and therein and outer member 33 therearound is then fitted into a liner sleeve or stator 45 of the same general construction as the liner sleeve 8 in Fig. 1.

Said sleeve is is formed with diametrically opposed transverse slots 47 and 48 through the wall thereof respectively communicating with the ports Q3 and in the case 5|. Journalled in said case for rotation about an axis eccentric to the axis of sleeve 45 and rotor is a drive shaft having a square cross-section portion 52 non-rotatably and transversely slidably extending through the respective rectangular openings 3i} and 44 in the pistons 32 and Ill}.

Inasmuch as the operation of the unit illustrated in Figs. 4 and 5 is the same as Figs. 1-3, repetition thereof is not deemed necessary.

A further modification of the present invention as illustrated in Figs. 6 and 7 comprises case parts 55 and 56 secured together as by bolts 51 and defining therebetween a cylindrical chamber in which is disposed a rotary liner sleeve 58 transversely grooved on its inner surface as at 55 along diametrically opposed areas.

Having a running fit and seal within the eccentrically disposed bore in said liner sleeve 58 is a piston-carrying sleeve 60 formed with a plurality of uniformly spaced openings 6! radially through the wall thereof, there being preferably four such openings respectively leading into the piston chambers formed within said sleeve 56 as by axially extending grooves broached or milled in said sleeve. For purposes of illustration, the intersecting pistons 62 re ciprocable in such chambers are the same as illustrated in Figs. 1-3. The openings 6! in sleeve 60 alternately communicate with the slots or grooves 59 in sleeve 58 and with ports 63 and 64 in case part 56 by way of an opening 55 adjacent one end of each groove 59.

Non-rotatably but transversely slidably extending through the rectangular openings 68 in said pistons is a square cross-section shaft 51 which is fixedly secured to case part 55 as by a lock nut 98 threaded onto one end of said shaft which extends through an opening 69 in case part 55. Said shaft 8'! has a non-circular crosssection portion 10 thereon fitting within a complementary recess 7! also in said case part 55 whereby to hold the shaft 6'! against rotation.

In this embodiment of the invention the driving of the unit to effect displacement of fluid thereinto and therefrom is effected by a drive shaft 12 journalled in a bearing 73 in case part 55 and having a toothed flange 14 integral therewith or fixed thereonto formed with teeth engaging in complementary notches formed in the end of sleeve member 58. The cylindrical wall 15 of the liner sleeve 58 with which the outer wall of sleeve Ell has a running fit is disposed eccentrically with respect to the axis of the drive shaft #2 and the square shaft 61 whereby rotation of said shaft 13 induces actuation of the sleeve 66 radially with respect to the pistons 62 on shaft 6?.

Thus, when this unit is operated as a pump, rotation of drive shaft 12 will cause rotation of the sleeve member 5-8 and successively cause openings Bl to communicate with the slots or grooves 59. During such rotation, pistons 62 will each be reciprocated radially in sleeve mem-' ber 68 thereby alternately drawing fluid into and discharging fluid from the piston chambers in said sleeve member, the displacement being in accordance with the eccentricity of cylindrical wall i5 relative to the axis of rotation of shaft l2. If desired, suitable means may be provided for adjusting the eccentricity.

Although the unit illustrated in Figs. 6 and 7 employs pistons 52 and a sleeve 60 similar to the pistons l6 and rotor sleeve It in Figs. 1-3, it will be understood that the pistons and it in Fig. 5 together with the sleeves 3| and 33 might be similarly employed in this construction wherein a square shaft is non-rotatably and transversely slidably connected to pistons and is nonrotatably secured to the case of the unit and a liner sleeve is rotated to cause desired actuation of said pistons in a non-rotary piston-carrying member or sleeve.

Referring now to the unit illustrated in Figs. 8-10, the same comprises case parts 83 and El defining a cylindrical chamber '82 in which is disposed a liner sleeve 83 and washers or end plates B l, said sleeve and washers being of bearing metal and the former being formed with circumferentially extending slots 85 and 36 therethrough respectively communicating with the in- 6 take and discharge ports 81 and 88 in said case part 80.

Journalled in said casing as in the bearings 89 and 90 in the respective case parts 89 and 8! for rotation about an axis eccentric of the axis of liner sleeve 83 is a drive shaft 9| formed with a square cross-section portion 92 intermediate its ends and a collar portion 93 adapted to abut and slide against the end face of bearing 89. Said drive shaft 9! is preferably provided with a passage 94 therethrough communicating at one end with a passage 95 which leads to the intake or low pressur side of the unit whereby to preclude building up of pressure in the chamber 96 by leakage and consequent undesired axial thrust on said drive shaft.

The square portion 92 of said drive shaft has a non-rotatable but transversely slidable fit with the rectangular cross-section bores 9i and 98 respectively formed in the perpendicularly disposed pistons 98 and E86, such transverse sliding being along the long sides of the rectangular bores and at right angles to the axes of the respective pistons. Said pistons are of cylindrical form with the opposite ends of each having a close sliding fit within bores HM and H32 diametrically through a piston-carrying member or sleeve I83, said member H153 having a close running fit within liner sleeve 83 and end plates 34.

As now apparent, the offsetting of the axes of bores lfil and [32 while axially lengthening the unit as a whole permits ready assembly of the pistons 99 and we in member H13 without requiring a detachable piston head as in the construction illustrated in Figs. 4 and 5. Furthermore, the provision of pistons 95 and Hill with relatively thick web portions has the effect of reducing the unit stresses on the walls of square portion 92 of drive shaft s! and bores er and t8. Piston 99 is formed with a transverse slot Hi l, the bottom of which slidably engages the side of piston Hill to thus preclude turning of piston 99. Such slot is of width suiiicient to allow reciprocation of said piston 99. Piston [til is prevented from turning as by a flat wall 5E5 formed therein engaged with the collar 93 on drive shaft 95.

The operation of the unit illustrated in Figs. 8-10 is generally the same as the other units. It is to be noted that when the drive shaft is rotated clockwise as viewed in Fig. 8, the fluid under pressure in the discharge port 8'! will have the effect of urging the pistons 93 and Hit, the drive shaft 9| and the piston carrying member [93 toward the left whereby the latter will form a more effective seal with liner sleeve 83 whereby to assure pressure sealing of the intake side of the pump.

The unit illustrated in Figs. 11-l3 comprises case parts Hi! and Ill forming a cylindrical chamber in which is fixed a liner sleeve H2 formed with circumferentially extending slots H3 and lid through the wall thereof respectively communicating with the ports i l5 and H6 formed in case part Hi3. Having a running fit with said sleeve E E2 is a piston carrying member ill generally the same as member 563 in Figs.

tion thereof has been omitted.

In this case, the square shaft 122 which nonrotatably and transversely slidably fits in the rectangular openings through the respective pistons I and I2I is itself rotatable on an eccentric shaft I23, said. shaft having one end fitted in a bearing I24 carried in member Ill and the other end extending through case part I I I with a radially extending arm I keyed thereto. Said arm is provided with a movable plunger I25 adapted to enter a desired one of the series of holes I21 formed in the case part III.

From the foregoing, it can be seen that with the member ill driven clockwise, for example, as viewed in Fig. 12, fluid will be drawn in through port lit and discharged through port H3 by the actuation of the pistons I2 and I2I. Now, if the arm I25 is shifted counter-clockwise, let us say 90, the displacement of the unit will be zero because each piston will draw in and expel fluid while in communication with port I I4 and will expel and draw back fluid while in communication with port II3. Of course, with the arm I25 at some intermediate position the displacement of the unit will be between zero and maximum.

On the other hand, if the arm I25 is turned 180 r from the position shown, then the unit will be reversed without necessitating reversal of the direction of rotation of member III, that is the port lid will be the discharge port and port II3 the intake port. Similarly, by positioning of said arm between 90 and 180 there will be effected a displacement between zero and maximum. In any event, while the total piston movement does not ever change, there is effected a change in the displacement because of the mover;

ment of each piston in only one direction while communicating with one port for maximum displacement, the movement of each piston equal distances in opposite directions while communicating with one port for zero displacement, and the movement of each piston unequal distances in opposite directions while communicating with one port for displacement between zero and maximum.

It is to be understood that the displacement varying and reversing mechanism is merely typical and that other mechanisms may be substituted to provide for finer or closer adjustment than possible with the holes I27.

A still further modification of the present invention is the arranging of the pistons so as to balance the loads on the drive shaft, one such arrangement being shown somewhat schematically in Fig. i l as comprising perpendicularly disposed pistons 36 and I3! similar to the pistons 89 and tilt? in Fig. 9 carried in a member I32, said member i1 2 being rotatable in a liner sleeve i323 about an axis i3i eccentric of the axis I of the square drive shaft I36.

In order to balance the loads imposed on shaft I35 by discharge of fluid under pressure by piston 5353 there is disposed thereadjacent and parallel thereto a piston I3! fitted on shaft I36 and carried in a member i238 which is also rotatable within liner sleeve E33 but about an axis I39 eccentric of drive shaft axis I35 but on the side thereof opposite the axis H34 of member I32 Similarly, the piston i3I is balanced by a piston i id carried in a member I4: parallel thereto and thereadjacent, said member MI being eccentric to member E32 whereby said pistons I3I and I40 move in opposite directions during the intake strokes and during the discharge strokes. Obviously said liner sleeve H3 and the casing therearound (not shown) will be provided with port 8. ing so arranged that fluid will be simultaneously drawn into the unit by each pair of parallel pistons I30-I 31 and I3II40 and simultaneously discharged from the unit by each pair of said pistons.

Having thus described several embodiments of the present invention it will be apparent to those skilled in the art to variously modify the same and to incorporate therein any of the displacement adjusting devices or schemes disclosed in my copending applications Serial Nos. 56,489 new Patent No. 2,537,349 issued on January 9, 1951 and 56,490 now Patent No. 2,574,921 issued on November 13, 1951 which were filed on October 26, 1948.

Other modes of applying the principle of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims, or the equivalent of such, be employed.

1 therefore particularly point out and distinctly claim as my invention:

1. In a piston pump, the combination of a case formed with a cylindrical chamber and circumferentially spaced fluid intake and discharge passages leading to such chamber, a cylindrical member supported in said case for rotation about its central axis and formed with at least two radially disposed piston chambers apart arranged to successively communicate with the passages in said case during rotation of said memher, a piston in each such piston chamber extending radially inward of said cylindrical memher, and a shaft member mounted in said case for rotation about an axis eccentric to the axis of said cylindrical member, said shaft member extending through one piston into the other and having a non-rotatable and transversely slidable connection with said pistons whereby to eifect reciprocation of said pistons radially in such piston chambers responsive to rotation of said cylindrical and shaft members, each of said pistons being formed with a lateral opening of noncircular cross section therethrough which opening provides parallel opposite sides perpendicular to the path of reciprocation of said piston, and

'said shaft member being of rectangular cross section having non-rotatable and transversely slidable engagement with the parallel opposite sides of the lateral opening in each piston.

2. In a piston pump, the combination of relatively rotatable inner and outer cylindrical members respectively formed with two pairs of diametrically opposed and radially disposed piston chambers and with fluid intake and discharge passages arranged to successively communicate with such chambers during relative rotation of said members, two pistons diametrically across said inner member each having its opposite ends reciprocable in one pair of such chambers, and another member extending through one piston into the other and having a non-rotatable and transversely slidable connection with an intermediate portion of said pistons and disposed eccentrically with respect to said inner and outer members, each of said istons being formed with a lateral opening of non-circular cross section therethrough which opening provides parallel opposite sides perpendicular to the path of reciprocation of said piston, and said another member being of rectangular cross section having non-rotatable and transversely slidable engagement with the parallel opposite sides of the lateral opening in each piston.

3. In a piston pump, the combination of a case formed with a cylindrical chamber and circumferentially spaced fluid intake and discharge passages leading to such chamber, a cylindrical member in such chamber and supported in said case for rotation about its central axis and formed with two pairs of diametrically opposed piston chambers arranged to successively communicate with the passages in said case during rotation of said member, two pistons diametrically across said member each having its oppo site ends reciprocable in one pair of such chambers, and a shaft member journalled in said case for rotation about an axis eccentric to the axis of said cylindrical member, said shaft member extending through one piston into the other and having a non-rotatable and transversely slidable connection with an intermediate portion of said pistons whereby to effect reciprocation of said pistons radially in such piston chambers responsive to rotation of said cylindrical and shaft members, each or said pistons being formed with a lateral opening of non-circular cross section therethrough which opening provides parallel opposite sides perpendicular to the path of reciprocation of said piston, and said shaft member being of rectangular cross section having non-rotatable and transversely slidable engagement with the parallel opposite sides of the lateral opening in each piston.

i. In a piston pump, the combination of relatively rotatable inner and outer cylindrical members respectively formed with four radially disposed piston chambers 90 apart and with fluid intake and discharge passages arranged to successively communicate with such chambers during relative rotation of said members, a pair of pistons diametrically across said inner member each having its opposite ends reciprocable in one pair of diametrically opposed piston chambers, and another member extending through one piston into the other and having a non-rotatable and transversely slidable connection with an intermediate portion of each of said pistons and disposed eccentrically with respect to said inner and outer members, each of said pistons being formed with a lateral opening of non-circular cross section therethrough which opening provides parallel opposite sides perpendicular to the path of reciprocation of said piston, and said another member being of rectangular cross section having non-rotatable and transversely slidable engagement with the parallel opposite sides of the lateral opening in each piston.

5. In a piston pump, the combination of a case formed with a cylindrical chamber and circumferentially spaced fluid intake and discharge passages leading to such chamber, a cylindrical memher in such chamber and supported in said case for rotation about its central axis and formed with four radially disposed piston chambers spaced 913 apart arranged to successively communicate with the passages in said case during rotation of said member, a pair of pistons diametrically across said member each having its opposite ends reciprocable in one pair of diametrically opposed piston chambers, and a shaft member journalled in said case for rotation about an axis eccentric to the axis of said cylindrical member, said shaft member extending through one piston into the other and having a non-rotatable and transversely slidable connection with an intermediate portion of each of said pistons whereby to effect reciprocation of said pistons radially in such piston chambers responsive to rotation of said cylindrical and shaft members,

each of said pistons being formed with a lateral opening of non-circular cross section therethrough which opening provides parallel opposite sides perpendicular to the path of reciprocation of said piston, and said shaft member being of rectangular cross section having nonrotatable and transversely slidable engagement with the parallel opposite sides of the lateral opening in each piston.

6. In a piston pump, the combination of a case formed with a cylindrical chamber and circumferentially spaced fluid intake and discharge passages leading to such chamber, a cylindrical member in such chamber and supported in said case for rotation about its central axis and formed with four radially disposed piston chambers spaced apart arranged to successively communicate with the passages in said case during rotation of said member, a pair of pistons diametrically across said member each having its opposite ends reciprocable in one pair of diametrically opposed piston chambers, a shaft member journalled in said case for rotation about an axis eccentric to the axis of said cylindrical member, said shaft member extending through one piston into the other and having a non-r0.- tatable and transversely slidable connection with an intermediate portion of each of said pistons whereby to eiiect reciprocation of said pistons radially in such piston chambers responsive to rotation of said cylindrical and shaft members, and means for varying the displacement of said pistons, each of said pistons being formed with a lateral opening of non-circular cross section therethrough which opening provides parallel opposite sides perpendicular to the path of reciprocation of said piston, and said shaft member being of rectangular cross section having non-rotatable and transversely slidable engagement with the parallel opposite sides of the lateral opening in each piston.

7. In a piston pump, the combination of a case formed with a cylindrical chamber and circumferentially spaced fluid intake and discharge passages leading to such chamber, a hollow cylindrical member having a close running fit in such chamber and supported in said case for rotation about its central axis, said member being formed with at least two radially disposed grooves 90 apart on its inner surface extending axially therethrough and with a passage opening into each such groove arranged to successively communicate with such intake and discharge passages in said case during rotation of said member therein, two pistons each reciprocable in one of such grooves radially of said member and extending radially inward of said member, and a drive member mounted in said case for rotation about an axis eccentric to the axis of said cylindrical member, said drive member extending within said cylindrical member and through one piston into the other and having a non-rotatable and transversely slidable connection with said pistons, each of said pistons being formed with a lateral opening of non-circular cross section therethrough which opening provides parallel opposite sides perpendicular to the path of reciprocation of said piston, and said drive member being of rectangular cross section having non-rotatable and transversely slidable engagement with the parallel opposite sides of the lat eral opening in each piston.

8. In a piston pump, the combination of a case formed with a cylindrical chamber and circumierentially spaced fluid intake and discharge pas- 11 sages leading to such chamber, a hollow cylindrical member having a close running fit in such chamber and supported in said case for rotation about its central axis, said member being formed with two pairs of diametrically opposed radially disposed grooves on its inner surface extending axially therethrough and spaced 90 apart and. with similarly spaced passages opening into the respective grooves arranged to successively communicate with such intake and discharge passages in said case during rotation of said member therein, a pair of intersecting pistons diametrically across said member each having its opposite ends reciprocable in one pair of diametrically opposed grooves radially of said member, and a drive member mounted in said case for rotation about an axis eccentric to the axis of said cylindrical member, said drive member extending within said cylindrical member through onepiston into the other and having a non-rotatable and transversely slidable connection with an intermediate portion of each or said pistons, each of said pistons being formed with a lateral opening or" non-circular cross section therethrough which opening provides parallel opposite sides perpendicular to the path of reciprocation of said piston, and said drive neinber being of rectangular cross section having non-rotatable and transversely slidable engagement with the parallel opposite sides of the lateral opening in each piston.

9. In a piston pump, the combination of a case formed with a cylindrical chamber and circumferentially spaced fiuid intake and discharge assages leading to such chamber, a hollow cylindrical member having a close running fit in such chamber and supported in said case for rotation about its central axis, said member being formed with at least two radially disposed bores 90 apart of circular cross-section providing two piston chambers arranged to' successively communicate with such passages during rotation of said member, two pistons each reciprocable in one of such bores radially of said member and extending radially inward of said member, and a shaft member mounted in said case for rotation about an axis eccentric to the axis of said cylindrical member, said shaft member extending Within said cylindrical member and through one piston into the other and having a non-rotatable and transversely slidable connection with said pistons, each of said pistons being formed with a lateral opening of non-circular cross section there through which opening provides parallel opposite sides perpendicular to the path of recipro cation of said piston, and said shaft member be-- ing of rectangular cross section having non-rotatable and transversely slidable engagement with the parallel opposite sides of the lateral opening in each piston.

10. In a piston pump, the combination of a case formed with a cylindrical chamber and circumferentially spaced fluid intake and discharge passages leading to such chamber, a hollow cylindrical member having a close running fit in such chamber and supported in said case for rotation about its central axis, said member being formed with two pairs of diametrically opposed radially disposed bores spaced 90 apart and arranged to successively communicate with such passages during rotation of said member, a pair of pistons diametrically across said member each having its opposite ends reciprocable in one pair of diametrically oppcsed bores radially of said memher, and a shaft member mounted in said case for rotation about an axis eccentric to the axis of said cylindrical member, said shaft member extending within said cylindrical member and through one piston into the other and having a non-rotatable and transversely slidable connection with an intermediate portion of each of said pistons, each of said pistons being formed with a lateral opening of non-circular cross section therethrough which opening provides parallel opposite sides perpendicular to the path of reciprocation of said piston, and said shaft member being of rectangular cross section having non-rotatable and transversely slidable engagement with the parallel opposite sides of the lateral opening in each piston.

11. In a piston pump, the combination of a case formed with a cylindrical chamber and circumferentially spaced fluid intake and discharge passages leading to such chamber, a hollow cylindrical member having a close running fit in such chamber and supported in said case for rotation about its central axis, said member being formed with two pairs of diametrically opposed radially disposed bores spaced 90 apart and arranged to successively communicate with such passages during rotation of said member, a pair of intersecting pistons diametrically across said member each having its opposite ends reciprocable in one pair of diametrically opposed bores radially of said member, and a shaft member mounted in said case for rotation about an axis eccentric to the axis of said cylindrical member, said shaft member extending within said cylindrical member and through one piston into the other and having a non-rotatable and transversely slidable connection with an intermediate portion of each of said pistons, each of said pistons comprising heads of circular crosssection closely fitting in such bores and an intermediate Web connecting said heads together, one of said heads of one piston being detachably connected to the web thereof whereby to enable assembly of said pistons in intersecting relation within said cylindrical member, each of said pistons being formed with a lateral opening of non-circular cross section therethrough which opening provides parallel opposite sides perpendicular to the path of reciprocation of said piston, and said shaft member being of rectangular cross section having non-rotatable and transversely slidable engagement with the parallel opposite sides of the lateral opening in each piston.

12. In a piston pump, the combination of a case formed with a cylindrical chamber and circumferentially spaced fluid intake and discharge passages leading to such chamber, a sleeve memer rotatable in such chamber about an axis coinciding with the axis of such chamber and formed with passages successively communicating with the passages in said case during rotation or" said member and with a cylindrical bore disposed eccentric to the axis of rotation of said member, a cylindrical member having a close running fit within such bore and formed with at least two radially disposed piston chambers 90 apart arranged to successively communicate with the passages in said sleeve member during rotation of the latter, two pistons each reciprocable in one of such piston chambers radially of said cylindrical member, and a member fixed in said case extending through one piston into the other and having a non-rotatable and transversely slidable connection with said pistons, each of said pistons being formed with a lateral opening of noncircular' cross section therethrough which opening provides parallel opposite sides perpendicular to the path of reciprocation of said piston, and said last-named member being of rectangular cross section having non-rotatable and trans versely slidable engagement with the parallel opposite sides or" the lateral opening in each piston.

13. In a piston pump, the combination of a case formed with a cylindrical chamber and circumferentially spaced fluid intake and discharge passages leading to such chamber, a sleeve member rotatable in such chamber about an axis coinciding with the axis of such chamber and formed with passages successively communicating with the passages in said case during rotation of said member and with a cylindrical bore disposed eccentric to the axis of rotation of said member, a cylindrical member having a close running fit within such bore and formed with two pairs of diametrically opposed piston chambers 90 apart arranged to successively communicate with the passages in said sleeve member during rotation of the latter, a pair of intersecting pistons diametrically across said cylindrical member each having its opposite ends reciprocable in one pair of diametrically opposed piston chambers radially of said cylindrical member, and a member fixed in said case extending through one piston into the otherand having a non-rotatable and transversely slidable connection with an intermediate portion of each of said pistons, each of said pistons being formed with a lateral opening of non-circular cross section therethrough which opening provides parallel opposite sides perpendicular to the path of reciprocation of said piston, and said last-named member being of rectangular cross section having non-rotatable and transversely slidable engagement with the parallel opposite sides of the lateral opening in each piston.

14. In a piston pump, the combination of a case formed with a cylindrical chamber and circumferentially spaced fluid intake and discharge passages leading to such chamber, a hollow cylindrical member having a close running fit in such chamber and supported in said case for rotation about its central axis, said member being formed with two pairs of diametrically opposed radially disposed bores spaced 90 apart and arranged to successively communicate with such passages during rotation of said member, a pair or". pistons diametrically across said member each having its opposite ends reciprocable in one pair of diametrically opposed bores radially of said member, and a shaft member mounted in said case for rotation about an axis eccentric to the axis of said cylindrical member, said shaft member extending within said cylindrical member and through one piston into the other and having a non-rotatable and transversely slidable connection with an intermediate portion of each of said pistons, said pistons and shaft member being formed with interengaging faces arranged to hold said pistons in predetermined rotative positions in such bores, each of said pistons being formed with a lateral opening of non-circular cross section therethrough which opening provides parallel opposite sides perpendicular to the path of reciprocation of said piston, and said shaft member being of rectangular cross section having non-rotatable and transversely slidable engagement with the parallel opposite sides of the lateral opening in each piston.

15. In a piston pump, the combination of a case formed with a cylindrical chamber and circumferentially spaced fluid intake and discharge passages leading to such chamber, a hollow cylindrical member having a close running fit in such chamber and supported in said case for rotation about its central axis, said member being formed with two pairs of diametrically opposed radially disposed bores spaced apart and arranged t0 successively communicate with such passages during rotation of said member, a pair of pistons diametrically across said member each having its opposite ends reciprocable in one pair of diametrically opposed bores radially of said member, and a shaft member mounted in said case for rotation about an axis eccentric to the axis of said cylindrical member, said shaft member extending within said cylindrical member and through one piston into the other and having a non-rotatable and transversely slidable connection with an intermediate portion of each of said pistons, one piston having a cutaway side portion to embrace the other piston and to retain said one piston in a predetermined rotative position with respect to the bores in which the same is reciprocable, said other piston being similarly formed with a cutaway side portion, and said shaft member being provided with a collar portion engaging the cutaway ortion of said other piston whereby to hold said other piston against turning in t -e bores in which said other piston is reciprocable, each of said pistons being formed with a lateral opening of non-circular cross section therethrough which opening provides parallel opposite sides perpendicular to the path of reciprocation of said iston, and said shaft member being of rectangular cross section having non-rotatable and transversely slidable engagement with the parallel opposite sides of the lateral opening in each piston.

16. In a piston pump, the combination of a case formed with a cylindrical chamber and circumferentially spaced fluid intake and discharge passages leading to such chamber, a cylindrical member supported in said case for rotation about its central axis and formed with at least two radially disposed piston chambers 90 apart arranged to successively communicate with the passages in said case during rotation of said member, two pistons, one in each of such piston chambers extending radially inward of said cylindrical member, a shaft member mounted in said case for rotation about an axis eccentric to the axis of said cylindrical member, said shaft member extending through one piston into the other and having a non-rotatable and transversely slidable connection with said pistons whereby to effect receiprocation of said pistons radially in such piston chamber responsive to rotation of said cylindrical and shaft members, said shaft member including an inner portion provided with trunnions coaxial with said cylindrical member, and means for rotating and locking said inner portion at a selected rotary position whereby to vary the displacement of the pump as desired, each of said pistons being formed with a lateral opening of non-circular cross section therethrough which opening provides parallel opposite sides perpendicular to the path of reciprocation of said piston, and said shaft member being of rectangular cross section having non-rotatable and transversely slidable engagement with the parallel opposite sides of the lateral opening in each piston.

17. In a piston pump, the combination of an outer member providing a cylindrical chamber and fluid intake and discharge passages leading into such chamber, and a rotor assembly rotatable in such chamber about the central axis of such chamber and provided with passage means successively communicating with such intake and discharge passages during rotation of said rotor assembly, said rotor assembly comprising a tubular member formed with perpendicularly disposed bores diametrically therethrough, the axes of such'bores being offset axially of said tubular member, a pair of cylindrical pistons reciprocable in the respective bores radially of said tubular member, and a drive shaft eccentric with such tubular member having a nonrotatable, transversely slidable connection with said pistons whereby to rotate said tubular member and to reciprocate said pistons therewithin, said pistons each having cylindrical ends, and one of said pistons having a recess on one side embracing the side of the other piston whereby to hold said one piston against rotation in its bore and to permit insertion of said one piston into its bore, followed by insertion of the other piston into its bore.

18. The pump according to claim 1'? further characterized in that said other piston and said drive shaft are formed with juxtaposed surfaces holding said other piston against rotation in its bore.

19. The pump according to claim 17 further characterized in that said drive shaft extends through said pistons and has both ends supported for rotation about such eccentrically disposed axis.

20. In a piston pump, the combination of coaxial, relatively rotatable inner and outer members, said inner member being formed with at 16' least two radially disposed piston chambers apart, saidouter member being formed with fluid intake and discharge passages arranged to successively communicate with such chambers during relative rotation of said members, a radial piston reciprocable in each such chamber and formed with a lateral opening of non-circular cross section therethrough which opening provides parallel opposite sides perpendicular to the path of reciprocation of said piston in such chamher, and a single shaft of rectangular cross section having non-rotatable and transversely slidable engagement with the parallel opposite sides of the'lateral opening in each piston, said shaft being disposed eccentricaily with respect to said inner and outer members.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,409,097 Guinard Mar. 7, 1922 1,729,764 Dinesen Oct. 1, 1929 1,867,198 Waite July 12, 1932 1,909,045 Davis et al. May 16, 1933 2,248,452 Erickson July 8, 1941 2,288,833 Pascoe July 7, 1942 2,503,257 Graham Apr. 11, 1950 FOREIGN PATENTS Number Country Date 26,111 Australia 1930 

